A thermoplastic polyester resin typified by polyalkylene terephthalate and the like has been widely used for parts of electric/electronic devices, automobiles, and the like due to the outstanding properties. In recent years, a demand for the safety against fire tends to be severer particularly in the electric/electronic devices and the number of examples in which resin materials to be used in the parts configuring the electric/electronic devices are required to have high flame retardancy increase. Heretofore, in imparting flame retardancy to resin materials, halogen containing flame retardants have been used in many cases because the properties thereof are easily balanced with other physical properties. However, the use of the halogen containing flame retardant has posed problems, e.g., a case of generation of acidic gas in incineration processing of resin parts, a case of generation of poisonous gas on a fire spot, and marine pollution. Therefore, due to an increase in the environmental awareness in recent years, a demand for halogen-free flame retardancy has increased, and thus it has been demanded to impart halogen-free flame retardancy to resin materials.
As general halogen-free flame retardancy imparting methods, a method for imparting frame retardancy using metal hydroxides and a method for imparting frame retardancy using phosphorus are mentioned. However, the metal hydroxides have disadvantages in that the metal hydroxides cannot impart frame retardancy unless a large amount of the metal hydroxides are compounded and also when a large amount of the metal hydroxides is compounded, the dynamic characteristics decrease. As the method for imparting frame retardancy using phosphorus, a method for imparting frame retardancy using red phosphorus and a method for imparting frame retardancy using organic phosphorus are known. When red phosphorus is used, the capability to impart flame retardancy is high but the handling thereof is difficult, e.g., generation of poisonous phosphine gas due to moisture and heat generated during drying and processing and the like. On the other hand, as the method for imparting frame retardancy using organic phosphorus, examples using (condensed) phosphate ester and phosphazene are known. Among the above, the (condensed) phosphate ester is an oligomer, and therefore bleed-out occurs after molding and the original flame retardancy is lost by bleed-out or volatilization of frame retardant components in a high temperature environment in some cases. Phosphazene has high heat resistance but is disadvantageous in that phosphazene is expensive.
In recent years, the utilization of electronic control and electric drive has increased in various applications including automobiles and the use thereof at a higher voltage has increased. Therefore, members to which polyalkylene terephthalate resin is applied tend to be required to have high tracking resistance. Accordingly, a polyalkylene terephthalate resin composition excellent in flame retardancy required as electric products has been increasingly required.
In particular, since the operating temperatures of the electric/electronic devices typified by an OA fixing device, a transforming device, a power module device, an inverter device, and the like are high and the devices are exposed also to high voltages, the balance among heat resistance, flame retardancy, and electrical properties is required also in resin materials to be used in parts thereof (hereinafter referred to as electric/electronic parts) and further a halogen-free flame retardancy imparting technique is also required.
For example, Patent Document 1 discloses Examples of a composition in which the flame-retardancy maintenance and the tracking resistance are improved using a polybutylene terephthalate resin and polyethylene terephthalate resin in combination with epoxy-modified styrene resin, phosphate ester, a triazine compound, a salt of cyanuric acid or isocyanuric acid, and talc (Table 3 of Paragraph [0131] and Paragraph [0143] of Patent Document 1). However, since the evaluation in a high flame-retardant test at 1/32 inch is V-1 and a large amount of phosphate ester and epoxy-modified styrene resin are compounded, the heat resistance is considered to be low, and therefore the composition has room for improvement.
Moreover, for example, Patent Document 2 discloses a resin composition in which an organophosphorus flame retardant of a specific structure and amorphous resin are compounded in a thermoplastic polyester resin but does not describe specific examples in the case of a polybutylene terephthalate (PBT) resin and the resin composition has room for improvement in terms of electrical properties.
Furthermore, Patent Document 3 discloses a resin composition in which a phosphorus flame retardant having a specific structure and at least one kind of amorphous thermoplastic resin selected from the group consisting of polyetherimide resin, polysulfone resin, and polyarylate resin are compounded in a thermoplastic polyester resin, for example, but does not describe specific examples in the case of polybutylene terephthalate (PBT) resin, and the resin composition has room for improvement in terms of electrical properties.